Structural analysis of hollow fiber dialysis membranes for clinical use.

Abstract

Little is knownof the structure of hollow-fiber dialysis membranesfor clinical use or of the effects of structure on solute and pure water permeability. Knowledgeof such aspects of membranestructure as pore radius, surface porosity, tortuosity and water content is required if the desired membranes are to be designed. The objective of the present study, therefore, is to obtain data on the pore radius, surface porosity and tortuosity of hollow-fiber dialysis membranesthrough an analysis of measured water content, and of solute and pure water permeability on the basis of a newly introduced tortuous pore model. In regenerated cellulose membranes, pore radius ranges from 21 to 34 x 10~10 m, and huge pores ranging in radius from 47 to 64 x 10"10 m are identified for EVAmembranes which are permeable to small amounts of serum protein. Values for surface porosity of the regenerated cellulose and EVAmembranes are approximately 33 and 22 %, and tortuosity is approximately 1.9 and 2.2, respectively. The tortuous pore model combined with the Lp and Pmmethod is well suited for elucidating the relationship between membranestructure and solute and pure water permeability.

Changes in the Porosity and Permeability of a Molecularly Imprinted Membrane Induced by the Adsorption of a Trace Quantity of Template

“…The observed changes in membrane permeability therefore more likely result from conformational changes, as indicated by the changes in solution uptake which correspond to variations in the porosity of the membrane. The permeability of creatinine across the MISSM measured during this study is lower than that across a low-flux type hemodialysis membrane (Cuporophane ® ) [24] with a pore diameter of 2-3 nm [25]. Since no macropores were observed in the MISSM during scanning electron microscopy (as shown in Fig.…”

Determination of pore radius of hollow-fiber dialysis membranes using tritium-labeled water.

“…Pore model studies on characterization of hydrophilic membranes for dialysis give lower values of pore radius and tortuosity, and higher values of surface porosity using 3H-water than using 14C-urea. 3. The method using 3H-water is suitable for characterizing dialysis membranesbecause of lack of adsorption of 3H-water on fully wetted or hydrophobic dialysis membranesand determination of Pm and Lwfor the same solute.…”

Evaluation of dialysis membranes using a tortuous pore model

“…Sakai et al (1985) introduced a tortuosity for the straight pore model proposed by Verniory et al (1973) that is obtained by exclusion of hydrodynamic resistance from a tortuous factor proposed by Mackie and Meares (1955) to account for the increased length of the solute path. This tortuous pore model makes it possible to explain the diffusive permeability of dialysis membranes for low molecular weight substances (Sakai et al, 1987(Sakai et al, , 1988. At larger molecular weights, however, the values predicted by the tortuous pore model begin to diverge from those obtained experimentally.…”

“…Diffusive permeability was measured at 310 K by means of a radioisotope technique (Sakai et al, 1987(Sakai et al, , 1988 in the case of HTO, and by means of a photoabsorption technique using optical fibers (Ohmura et al, 1989;Kanamori et al, 1994) in the case of the other solutes. Both of these methods are free from the influence of solute transfer due to convection and make it possible to measure permeability due solely to diffusion.…”